Almost all hair coloring methods use colorants (dyes, for example) that change the color of the hair and produce a single color from the treated hair. Coloring methods include methods for permanent coloring and methods for temporary coloring.
Permanent coloring methods typically use ammonia to open up a hair cuticle so that colorants may be deposited on the underlying hair cortex. Peroxide is used to drive formation of new color and to remove existing natural and artificial pigments.
Temporary methods also use colorants such as acidic dyes that do not significantly penetrate the cuticle. Temporary methods also don't use ammonia. Shampooing eventually washes out temporary colorants and the hair's natural pigment is retained. Ground silica suspended in a polymer has also been used to create a temporary iridescent effect.
Fiber coloration with little or no colorants occurs in nature. Peacock feathers, for example, are known to have little or no pigmentation. The striking colors in peacock feathers are produced primarily from diffraction of incident light from nanometer scale branches of the peacock feathers. Such an effect is desired for human hair.
Based on the forgoing, there is a need for a hair treatment process for providing dispersed colors by light diffraction on human hair.